1. Technical Field
The present invention relates to a technical field of an image forming device such as an electrophotographic device, an electrostatic copier, a printer, a facsimile, and the like in which a DC power supply for a process unit for each color is independently arranged and an AC power supply is commonly arranged for the process units for three colors in the full-color image forming device of a tandem type.
2. Related Art
Heretofore, as an image forming device of a plurality of colors or full-color of an electrophotographic system, so cold an image forming device of a tandem type has been proposed in which a photoreceptor is arranged in a tandem manner in accordance with for each color and a toner image of each color formed on each photoreceptor is sequentially overlapped on an intermediate transfer medium or a transfer material in order to form a color image (for example, see JP-A-2001-324850 (hereinafter, referred to as Patent Document 1)).
A charging voltage in which AC voltage and DC voltage are superimposed is applied to a charging roller in the charging device for each color in the image forming device of a tandem type disclosed in Patent Document 1. In this case, an AC voltage power source and a DC voltage power source are respectively independently arranged for each color.
However, in the image forming device disclosed in Patent Document 1, the AC voltage power supply and DC voltage power source are respectively independently arranged for each color, so that there are various problems in that a number of parts is increased, cost is increased, the size of the image forming device is increased, and the control thereof is complicated, or the like.
Consequently, in order to correspond with the various problems described above, the AC voltage power supply may be commonly provided to each process unit for three colors (yellow Y color, magenta M color, cyan C color) There is little possibility that the leakage of charging voltage is generated at the time when the photoreceptor is charged by the charging roller in the case where such an image forming device of tandem type is ordinarily used. However, when another object is contacted to the surface of the photoreceptor and damaged when the process unit including the photoreceptor is replaced by user, leakage is generated at the time of printing process and image forming defect is generated. Accordingly, it is necessary to replace the process unit in which leakage is generated. However, commonly providing the AC voltage power supply for each process unit for three colors makes it difficult to identify the process unit in which leakage is generated.